1. Field of the Invention
The present invention generally relates to a board holddown, and particularly to a board holddown for permanently holding a circuit board and detachably holding another circuit board.
2. Description of Prior Arts
Printed circuit boards are used extensively in various types of electrical equipments. Typically, board holddowns are employed to support and provide spacing for circuit boards. Board holddowns are used, for example, to separate, support and electrically insulate a printed circuit board from either a chassis or other printed circuit boards.
U.S. Pat. Nos. 4,966,482 and 4,712,939 disclose a substrate support of integral construction, by which a substrate can be fixed angularly to and optionally detached from a plate. The support comprises a base, a fixing portion for cooperating with the base and holding the plate therebetween, a first projection extending from the base, and a second projection extending from a wall extending from the base. The end of the substrate can be inserted into the space between the first projection and the second projection and the substrate can be fixed angularly to and optionally detached from the plate. However, particularly referring to FIGS. 6, 10 and 12 of the two patents, it can be readily seen that a plurality of fixation members are put in use together with the support. The fixation members are different in form from the substrate support and facilitate the substrate support to hold the substrate at a distance from the plate. Obviously, a single substrate support of this type without the separate fixation members could not securely hold the substrate and the plate together. Moreover, the integral substrate support is not reliable enough when subjected to vibration, shock, or other horizontally directed force for the wall is substantially perpendicularly formed with the base.
U.S. Pat. No. 4,701,984 discloses another type of board support. The board support comprises a mounting portion for holding a panel and a retainer portion extending beyond the mounting portion for insertion through an aperture of a printed circuit board. The board support also comprises a resilient retaining means adapted to yield upon passage through the aperture in the printed circuit board and thereafter to bear against the opposite surface of the printed circuit board to retain the printed circuit board in supported position spaced from the panel. However, the printed circuit board is easily disengaged from the board support when subjected to an accidentally occurred, vertical force for the board support holds the printed circuit board only through a slight distortion of the resilient retaining means.
Hence, an improved board holddown is highly desired to overcome the disadvantages of the prior art.
Accordingly, it is an object of the present invention to provide a board holddown by which a circuit board can be securely fixed to and easily detached from another circuit board.
In order to achieve the above-mentioned object, a board holddown in accordance with the present invention for fastening circuit boards, comprises an elastomeric support member and a bullet-shape member of more rigid material than the support member. The support member comprises a first mounting portion for supporting a first circuit board, a second mounting portion for supporting a second circuit board, and an elongate, thin neck projecting from the second mounting portion. The bullet-shape member is attached to the elongate, thin neck and comprises a latch abutting against the second circuit board and cooperate with the second mounting portion to thereby retain the second circuit board therebetween. The elongate, thin neck has substantial resilience so that the second circuit board can be easily detached from the board holddown by pushing the bullet-shape member away from its holding position.
Other objects, advantages and novel features of the invention will become more apparent from the following detailed description of the present embodiment when taken in conjunction with the accompanying drawings.